Midterm 3 Practice Test

1. Two blocks collide with a load bang, is mechanical energy conserved during the collision?

(a) No (b) Yes.

2. Three balls of mass 2 kg are placed at the origin, 2 m up the x-axis, and 2 m up the y-axis. What is xCM?

(a) 1 m (b) 2 m (c) 1/3 m (d) 2/3 m (e) 0 m

3. A 800 kg car is at the top of a 100m hill at which it has a speed va, it coasts down a valley and to the top of another 150m hill. Find va such that it reaches the higher hill with zero speed.

(a) 980 m/s (b) 31.3 m/s (c) 22.1 m/s (d) 48.3 m/s (e) 15.8 m/s

4. A 1500 kg car is traveling East at 30 m/s while another 2500 kg car, traveling in the same lane, heads West at 20 m/s . What is vCM?

(a) -1.25 m/s (b) -5000 m/s (c) 23.75 m/s (d) 95,000 m/s (e) -18 m/s

5. Two blocks of mass M and 2M are attached to the ends of a spring. The system is placed on a horizontal frictionless surface, compressed, and released. If v is the speed of the 2M block, what is the total kinetic energy of the system after the masses have flung apart? Neglect the spring mass.

(a) 2M v2 (b) 5M v2 (c) 4M v2 (d) 3M v2 (e)M v2

6. [written answer] A clay block of mass 100 kg and speed 3 m/s collides with a clay block of mass m at rest and sticks. During the collision 20% of the initial kinetic energy is dissipated in heat. Find m.

7. [written answer] A particle of mass m is travelling up the y-axis at speed v. It strikes a particle of mass M=400 gm (which was at rest), sending it flying to the right at an angle of 15 degrees with respect to the +y-axis. The original particle flies to the left at 25 degrees with respect to the +y-axis. Determine m.